Electronic indicating device



NOV. 3, 1936. GlBSON ET AL 2,059,575

ELECTRONIC INDICATING DEVICE Filed Feb. 28, 1954 W 7.' GIBSON AT7DR/VEY Y Patented Nov. 3, 1936 UNITED s'mras ELECTRONIC INDICATING DEVICE William T. Gibson and Donald H. Black, Aldwych,

London, England, assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application February 28, 1934, Serial No. 713,282 In Great Britain March 29, 1933 10 Claims.

The present invention relates to electronic indicating devices and more particularly to improvements in cathode ray tubes or devices.

An object of the invention is to facilitate visual indication of electrical phenomena.

A further object of the invention is to obtain a more sensitive control of the electron beam in discharge devices.

According to one feature of the present invention there is provided a cathode ray tube comprising a fluorescent screen which is supported within the tube from the stem thereof.

According to another feature of the present invention we provide a cathode ray tube in which an electron gun including an anode, a pair of deflecting plates, and a fluorescent screen are combined in a rigid unitary structure adapted to be assembled complete prior to mounting on the stem of the tube.

According to another feature of the invention, in a cathode ray tube a pair of deflector plates are provided which extend over the whole length of the cathode ray beam from the electron gun to the fluorescent screen.

Another feature of the invention is a cathode ray tube in which one of the deflector plates is curved in order to approximate the shape of the deflected beam of electrons over the whole of its length, thereby giving great sensitivity to the de-' vice.

Still another feature of the invention consists in the use, in a cathode ray tube, of a fluorescent screen comprising a metallic plate coated with fluorescent material. Preferably this metallic screen is connected directly to the anode in order that charges accumulating thereon may be dissipated.

The invention will be described with reference to the accompanying drawing which illustrates a preferred embodiment thereof, but it is to be understood that this is exemplary only, and the invention is not to be considered as limited thereto. Fig. 1 is a perspective view of a device made according to this invention with the enclosing vessel broken away to show the unitary electrode assembly;

Fig. 2 is a side View in elevation of the device shown in Fig. 1 to illustrate the relative position of the electrode assembly with respect to the stem; and

Fig. 3 is a cross-sectional view of the electron gun assembly showing the details of construction. I

The" tube herein described and illustrated is capable of producing a deflection of the fluorescent spot in one dimension only, the degree of deflection from its normal position providing an J The electron gun includes a small emissive cathode, such as a filament i8, which may be of the directly-heated type, arranged axially in a short metallic focusing cylinder I, as shown in Fig. The cathode is connected toa pair of leading-in wires 2. On the end of the focusing cylinder I, but insulated therefrom by a sheet of mica, is a flat metallic plate 3 having a small circular hole t coinciding with the axis of the focusing cylinder. The metallic plate 3 forms the anode, and when suitable potentials are applied to the various electrodes, a narrow beam of electrons is projected through the hole 4 along the axis thereof.

The electron gun is mounted on two rigid rods 5 and 6 one on each side of the focusing cylinder l, suitable mica insulating pieces I being provided so that the rods are insulated from one another and from the electron gun. One rod 5 is approximately straight, but the other rod, 6, is bent 20 outwards beyond the electron gun, and thus diverges from the rod 5. At the free ends of the rods is mounted a metallic screen 8, coated with fluorescent material on the side towards the electron gun. This screen is insulated from the rod 5 by a mica insert 9 but is in contact with the bent rod 8, which is also connected to the anode plate 3 of the tube.

The fluorescent screen 8 is inclined at an 0blique angle to the direction of the beam of electrons, so that good visibility of the spot is assured when looking in a direction almost normal to the screen, and almost perpendicular to the direction of the beam. The two deflector plates Ill and H consist of strips of metal extending from the anode 3 to the fluorescent screen 8. One plate in is fiat, and is insulated at the screen and at a point where it approaches the aperture in the anode by means of the mica pieces 9 and 1 respectively. The deflector plate H is attached to the anode on the opposite side of the central aperture and curves outwardly until it is joined to the bent rod 6 at the point of attachment of the screen.

It will thus be seen that the electron gun, the deflecting plates and the fluorescent screen are all assembled in a single rigid unit which can then be mounted complete on the stem of a tube by means of twoshort supports it and It sealed in the stem l4 and welded to the aforesaid rigid rods 5 and 6. The unit is mounted in an inclined position in the bulb l5 about the size of an ordinary radio receiving tube, so that the fluorescent screen is nearly vertical, and can be clearly viewed by looking horizontally through the side of the bulb. The tube may be provided with a suitable base it and contact pins ll.

Owing to the arrangement of the electron gun assembly with respect to the screen, the fluorescent spot in its undeflected. position is near the left-hand edge of the screen, and is deflected towards the right-hand edge under the influence of correctly applied deflecting potentials. Since the deflector plates Hi and H exert their effect over practically the whole length of the beam, the oscillograph is very sensitive. Moreover, the curvature of the plate ll insures that this plate is at an approximately constant distance from the beam in its more deflected position over the whole of the length of the beam, resulting in still greater sensitivity.

The use of a metallic plate as a fluorescent screen has several important advantages, one of these is that the electrons reaching the screen can now return directly to the anode. Previously in cathode ray oscillographs it has been customary to introduce into the tube a certain quantity of gas. This had two effects, it aided in producing a sharply defined spot to be obtained on the screen, and at the same time it allowed the charge accumulating on the fluorescent screen to escape. With a metallic fluorescent screen connected to a suitable source of potential, the electrons can escape directly, and a gas filling is unnecessary while in the small tubes which form the subject of the present invention, the focusing can be made sufficiently sharp without its aid. The tubes can, therefore, be arranged to operate in high vacuum.

There is a further important advantage in utilizing a flu-crescent screen of metal. The charge imparted to the screen by the beam of electrons can escape immediately. In the type of tube in which the fluorescent layer was provided on the glass of the tube, the charge did not always escape quickly enough, and hence the residual charge repelled the beam. It was, therefore, generally necessary to apply a fairly high voltage to the anode in order to endow the electrons in the beam with sufflcient energy to promote secondary emission from the screen to dissipate the charge in this manner. With a metal screen according to the present invention, this is unnecessary, and the anode voltage is reduced to that which is necessary to enable the electrons to cause fluorescence. Tubes have been constructed according to the present invention in which this voltage was as low as 110 volts.

What is claimed is:

l. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode, a fluorescent screen positioned at an angle with respect to the axis of said gun, and means joining the elements into a unit, and means supporting said unitary structure at an angle on said stem to view said screen through the side wall of said vessel.

2. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode, a fluorescent screen positioned at an angle with respect to the axis of said gun, and means joining the elements into a unit, means supporting said unitary structure on said stem in an angular position to view said screen through the side wall of said vessel, and a deflector plate extending longitudinally from said anode to said screen.

3. A cathode ray discharge device, according to claim 2, in which said deflector plate is electrically and mechanically connected to said anode and said screen.

4. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode, a pair of elongated deflector plates, a fluorescent screen positioned at an acute angle with respect to said plates, and means joining the elements into a unit, and wires connecting said unit to said stem and supporting said unit diagonally across the axis of said stem.

5. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure supported from said stem, said structure including an electron gun having a perforated anode, a pair of elongated deflector plates, and a fluorescent screen positioned at an angle with respect to said plates, said plates extending from said anode to said screen and being mounted in such relation that the distance therebetween increases from said anode to said screen.

6. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode, a pair of elongated deflector plates and a fluorescent screen, and means supporting said unit structure on said stem, one of said plates having an outward curvature from said perforated anode to one end of said screen and the other plate being flat.

7. A visual indicating device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode, and a fluorescent screen, and means supporting said unitary structure on said stem, the axis of said unitary structure being approximately at a degree angle with respect to said stem, and.the plane of said screen being substantially parallel to and offset with respect to the axis of said stem.

8. A visual indicating device comprising .an enclosing vessel having a stem, a unitary structure supported from said stem including an electron gun having a perforated anode, a metallic screen having a coating thereon, and supporting means connecting said screen to said gun, said screen being positioned at an acute angle with respect to the axis of said gun.

9. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure including an electron gun having a perforated anode having a metallic screen having a fluorescent coating thereon, a pair of rigid rods supporting said metallic screen at an angle with respect to the axis of said electron gun, and a pair of elongated deflector plates extending from said anode to said screen and positioned between said rods.

10. A cathode ray discharge device comprising an enclosing vessel having a stem, a unitary structure supported from said stem including an electron gun, a perforated anode, a fluorescent screen, a pair of rigid rods extending between said anode and screen, a pair of elongated deflector plates laterally arranged with respect to said rods, and insulating members on said anode and screen respectively, supporting one of said rods and one of said deflector plates from said anode and said screen.

WILLIAM T. GIBSON. DONALD H. BLACK. 

